Bath for producing etching-resists and process of preparing such bath.



UNITED STATES PATENT oFFIoE.

JOANNY AGARITHE DE-l'EY, OF ST.-MAURICE, FRANCE.

BATH FOR PRODUCING ETCHING-RESISTS AND PROCESS OF iREPARING SUCH BATH.

Specification of Letters Patent.

Patented Aug. 10, 1915.

N0 Drawing. Application filed April 27, 1912, Serial No. 693,722. Renewed April 3, 1915. Serial No. 19,090.

To all whom it may concern Be 1t known that I, JOANNY AGARITHE DEJEY, engineer, a subject of the Republic means, which layer has for its object to form an etching resist on the drawing transferred. All the blank spaces are thus covered with a layer of tin, which isnot attacked by the acids and the other agents employed for the engraving. When the said' process is applied to rollers for printing fabrics,- oilcloth, paper and the like,the transfer is-made by means-of a special machine, and the deposit of tin is madeover the wholeface of the cylinder, except at the places where the ink has been applied, the design being thus preserved with the greatest fidelity. If the ink forming'the design be then dissolved, either with benzin or spirits of turpentine, the copper will be found to appear at the place of the design, while the blanks remaincovered with a layer of tin, which is not affected. Under these conditions the roller presents the same condition as if the drawing or design had been'traced with a pantograph, with this difference, however, that in the pantograph the blanks are protected by varnish, while in my process they are protected by tin. The cylinder thus prepared is directly etched either with chromic acid or in a solution of cyanid of potassium by means of an electric current.

The present invention relates to an improved composition of the tin bath, enabling a perfectly close and non-porous deposit of this metal to be obtained, which is an absolutely indispensable condition for the carrying out of the process hereinbefore mentioned, The composition of this bath is as follows: 2 kilograms of sodium pyrophosphate are dissolved in 10 liters of boiling water. When the solution is complete there are added gradually, under constant agitation, 2 kilograms of tin salt, for instance,

stannousv chlorid. A white precipitate is About 10 liters of boiling water and 2 kilograms of sodium pyrophosphate are then added to the white precipitate. A limpid solution is formed, which is diluted in the tinning vat with the necessary quantity of cold water to form 100 liters. 200 grams of dry roasted fecula dissolved in a little hot water is then added and then 250 grams of pulverized tartaric acid, and finally 600 grams of chlorid of sodium. The bath is then ready for use.

Of course the copper roller or plate which is to be engraved must be thoroughly cleaned, in order to obtain a complete .adhesion. v

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

The process of preparing a bath for producing etching resists, which consists in dissolving 2 kilograms of sodium pyrophosphate in 10 liters water, then adding gradually 2 kilograms of a suitable tin salt, washing the precipitate thus obtained, adding 2 kilograms of pyrophosphate of soda and 10 liters boiling water to the said precipitate, diluting the solution thus formed, adding thereto a solution of 200 grams of roasted fecula in water, and 250 grams of tartaric acid, and finally adding 600 grams of chlorid sodium. I

H. C. Coxn, EDMOND DUSARGUES on COLOMBIER. 

